My take on the first presidential debate is fairly simple and does not require a lengthy exposition. I was disappointed but not surprised that Gary Johnson and Jill Stein were not invited to participate. I suspect that their involvement would have shown voters that they have other options besides the two candidates who were invited. Moreover, I think that their presence probably would have made both of the major party candidates look even less suited for the job than they did.
With that out of the way, I'll consider the question of who won the debate. I am doing this from the perspective of someone who does not support either of the two candidates who participated in the debate. I think there are three ways of looking at this question. First, we can set aside expectations of each candidate coming into the debate, focusing instead on the typical way of evaluating debate performance (e.g., the debaters' grasp of the subject matter, delivery, points scored against the opponent). Second, we can emphasize the pre-debate expectations, comparing how each debater performed relative to his or her expected performance. Third, we can focus on whether each debater accomplished the specific objectives he or she needed to accomplish, something that typically differs for each candidate and is expected to matter in the sense of attracting undecided voters.
Going by anything like the traditional standards of evaluating debate performance, it seems fairly clear that Hillary Clinton won and won decisively. That is not to say that it was a shut-out victory or that Donald Trump did not score some points along the way. I thought he held his own reasonably well for the first 20-30 minutes of the debate. And Clinton was far from perfect. She turned in what might have been a mediocre performance against an opponent who had bothered to prepare. But in this particular contest, she had no such opponent. If we use the criteria typically used to determine a winner, Clinton was our winner.
The question of context and expectations is an interesting one. Coming into the debate, there were very low expectations for Trump. In some circles, anything short of Trump throwing his own feces during the debate would be considered a victory. As noted above, Trump performed better than I expected him to for the first 20-30 minutes of the debate. He balanced this out, however, by performing far worse than I expected him to for the last 30 minutes or so. The expectations for Clinton were much higher. She's done this before and has a grasp of the issues her opponent clearly lacks. For the most part, she performed like I expected her to, probably even better. I was impressed with how she took the fight to Trump and exploited the weakness that is his ego. All in all, I'd have to say that even when the pre-debate expectations are emphasized, Clinton emerged as the winner. Trump was just too bad in too many important ways that should (but probably won't) be disqualifying.
Getting pragmatic, we can ask ourselves what each candidate needed to accomplish and how well each accomplished it. I think that the primary things Trump needed to do in this debate were to squash all the concerns about his temperament and demonstrate his ability to behave in a presidential manner. Basically, he needed to turn in the sort of debate performance that would lead undecided voters to be able to comfortably picture him as their president. I believe he failed miserably at this. For the majority of the debate, he came across as even less presidential than he has previously. I would not have predicted that this was possible, but there it was. I'm not sure Clinton fared much better. I think the primary things Clinton needed to do were to give voters some good reasons to support her aside from fear of Trump and to connect with voters emotionally by being more authentic than she has been willing to be so far in her campaign. I thought that she was somewhat effective on the first point and showed little progress on the second. While I do not think that either candidate did what they needed to do particularly well, Clinton came closer. I'd have to give her the win here as well.
As for my favorite moment in the debate, I suppose that would have to be when Trump whined about how Clinton's campaign was running ads that were "mean" to him. This coming from someone who has been behaving like Trump has throughout his entire campaign was just too much. There were many other good ones, but that was the one that stood out to me.